A light fixture (US English), light fitting (UK English), or luminaire is an electrical device used to create artificial light by use of an electric lamp. Light fixtures have a fixture body and a light socket to hold the lamp and allow for its replacement.
Fixtures may also have a switch to control the light, either attached to the lamp body or attached to the power cable. Permanent light fixtures, such as dining room chandeliers, may use a wall switch to turn them on and off; as such, these fixtures may have no switch on the fixture itself. Other fixtures, such as outdoor light poles, may be turned on and off by control of the power supplied thereto by a remotely located switching device.
Fixtures require an electrical connection to a power source, typically AC mains power, but may also have battery power for camping or emergency lights. Permanent light fixtures may be directly wired. Moveable lamps have a plug and cord so that they can be plugged into a wall socket.
Light fixtures may also have other features, such as reflectors for directing the light, an aperture (with or without a lens), an outer shell or housing for lamp alignment and protection, an electrical ballast or power supply, and a shade to diffuse the light or direct it towards a workspace (e.g., a desk lamp).
Portable light fixtures are often called “lamps”, as in table lamp or desk lamp. In technical terminology, the lamp is the light source, which is typically called the light bulb. The term “luminaire” is recommended by the International Electrotechnical Commission (IEC) for technical use.
One problem with light fixtures is that they require specialized equipment and a power source to accomplish only a single function. For example, if the amount of light required from a light fixture increases after the fixture has been installed, only limited increases in lumen output may be affected by increasing the wattage of the light bulb, which may be insufficient to meet the increased light output demand. Additionally, if it is desired to add a different type of device to be powered by the same power source, the light fixture typically will not accommodate the extra device, either as a replacement for the light bulb or to be mounted alongside the light bulb. The light fixture is therefore considered to be a single use device.